Patent Grant
9079243
The invention relates to a method of controlling or regulating a temperature as, in particular, in a secondary cooling in continuous casting installations.
In continuous casting installations, a strand of a cast product behind the mold is cooled to a complete solidification in so-called secondary cooling. This cooling plays a decisive role for the material quality of the strand. A complete solidification should take place within the roller segments of the continuous casting installation which support the strand with a liquid core. The object is to so measure the cooling rate of the strand cooling and the temperature region that the cast strand solidifies error-free.
In continuous casting installations according to the state of the art, cooling is realized by using spray water, wherein the amount of the spray water is controlled in accordance with spray water tables. These spray water tables contain, according to the state of the art, a separately determined amount of the cooling water for spray water for each cooling zone. For different casting speeds, a determined therefor, water amount is preset. Dependent on the material of the strand, an operator of the installation selects a suitable table that was drawn for adjusting the water amount in the secondary cooling. Handling of a large number of different tables for different operational condition during a working day of casting is expensive and time-consuming.
The object of the present invention is to provide a device for and a method of controlling or regulating the temperature and which should reduce or completely eliminate the drawbacks of the state of the art.
According to the invention, this object is achieved, with respect to the method, with a method of controlling or regulating a temperature of a cast strand in a casting installation with a control or regulation unit, in particular for controlling or regulating the temperature in a secondary cooling of the casting installation with at least one means of cooling the cast strand wherein dynamic change at least of a set temperature of the cast strand on the basis of data and/or signal which the control or regulation unit receives and/or determines.
Thereby, the following advantage is achieved that the set temperature for controlling the secondary cooling automatically and dynamically adapted to the actual facts. Thereby, it became at least partially unnecessary for the operator to handle numerous tables still necessary in the state of the art. The set temperatures, as a rule, are so preset that a normal operation with expected casting parameters (e.g., casting temperature, casting speed) is possible. Because in practice, these parameters, nevertheless, fall below or are exceeded or the change of the speed can result in diminishing of the quality of the to be treated material, the invention contemplates a dynamic adaptation of set temperatures to actual facts, i.e., to possibly changing casting parameters. When eventually the casting parameters are again in the expected range, the set temperatures are again adjusted to their initial values. This control/regulation of the set temperatures is carried out in an individual/separate module within the common control and regulation unit.
Data and/or signals, which the control or regulation unit receives or determines are, in particular, temperature values of the cast strand at least in one position, wherein the temperature value is either calculated or measured. In the case when calculation of the temperature value is carried out, in addition to the calculation, advantageously, measurement of the temperature of the strand can be carried out, for comparing the temperature calculation with the measurement.
The control or regulation unit determines, based on the received and determined data and/or signals, the condition of the cast strand at least in one position and controls or regulates in a second module, taken into the consideration the adapted set temperature and the requirements of the casting process, the temperature of the strand in the one position by suitable cooling.
It is advantageous when a dynamic adaptation of set temperature of the cast strand at least in the one position is carried out dependent on an exit temperature of the cast strand from a mold.
According to a further inventive idea, it can be advantageous when the control or regulation unit, based on determined and/or received data or signals, determines bending of the strand or of the strand shell between at least separate rollers. At that, it is advantageous when the control or regulation unit based on determined and/or received data or signals, determines elongation of the strand or the strand shell between at least separate rollers. It is also advantageous when a value of the determined bending and/or elongation is compared with a limiting value and upon exceeding the limiting value, a warning is issued. It is also advantageous when a value of the determined bending and/or elongation is compared with a limiting value and upon exceeding the limiting value, reduction of the set temperature of the strand is carried out in a region of the strand in which the excess is produced. Still further, it is advantageous when adaptation of the set temperature is carried out in such a way that, essentially, the bending and/or elongation do not exceed the limiting value in the entire region of the secondary cooling.
According to a further inventive idea, it is advantageous when the control or regulation unit based on determined and/or received data or signals, determines ductility of the strand. At that, it is beneficial when the determined ductility of the strand is compared with a limiting of the ductility value and upon exceeding the limiting value, a warning is issued. It is also advantageous when the determined ductility of the strand is compared with the value and upon exceeding the limiting value, and increase of the set temperature is triggered. It is further advantageous when the determination of the ductility of the strand is preferably carried out for a region in front of a bending and/or straightening unit of the casting installation.
According to a yet further inventive idea, it is advantageous when the control or regulation unit, based on determined and/or received data or signals, determines a solidification length of the strand. It is further advantageous when the determined solidification length of the strand is compared with a preset limiting value and upon exceeding the limiting value, an increase of the set temperature of the strand is triggered. It is further advantageous when the control or regulation unit so select the set temperature, that the limiting value is essentially reached.
With regard to the device, the object of the invention is achieved with a device for controlling or regulating a temperature of a cast strand in a casting installation with a control or regulation unit, in particular for controlling or regulating the temperature in a secondary cooling of the casting installation with at least one means of cooling the cast strand, wherein a dynamic change of at least one set temperature of the cast strand is carried out based on data and/or signals which the control or regulation unit receives and/or determines. This device, advantageously, can be used for carrying out the above-mentioned method.
The requirements to the secondary cooling are very diverse. E.g., a complete use of the available production capacity, e.g., the use of the available strand support for solidification length essentially up to the end, can constitute a control parameter.
During the regulation of the strand temperature, the calculated solidification length can be taken into consideration, when controlling or regulating the temperature or cooling.
As a further advantageous parameter for controlling cooling, achieving and maintaining of at least individual quality parameters of the strand can be used, wherein a portion of new steel grades is sensitive to unfavorable cooling course, so that the cooling rate constitutes here a control parameter in order to favorably influence the strip quality.
E.g., with the change of the casting speed, the strand temperature at the mold outlet also changes and the following cooling should take this into account, so that no quality problems, e.g., in form of too high thermal stresses, which can lead to fissures in many sensitive steel grades, arise.
With the use of temperature control or temperature regulation, it is advantageous when the set temperature for the cast strand is preset at different positions, and those can be adapted to changing conditions, based on changing parameters.
Further, the strand in the casting installation has a tendency to bulge between the supporting rollers. At a too large bulging, high bending stresses and inner elongation partially occur. Those again can lead to damage of the strand. The maximal allowable bulging advantageously depends on the preset casting parameters, e.g., from casting speed and/or casting temperature.
In the case when the strand is bent or straightened, the strand is subjected to additional elongations and stresses. The strand material, then, should be able to withstand the additional elongations and stresses, without formation of noticeable fissures. When the strand is brittle, surface fissures can be formed.
In order to prevent such fissures to a most possible extent, it is advantageous when the strand is bent or straightened in a temperature range in which the strand is suitably ductile.
Advantageous further developments are described in sub-claims.
Below, the invention will be described in detail based on an embodiment with limiting to the drawings. The drawings show:
The invention relates to control process or regulation process, in particular, for secondary cooling of a continuous casting installation. To this end,
The continuous casting installation 1 has, in addition to the control and regulation unit 3, also means 4, 5 for acquisition of data or signals such as, e.g., sensors. E.g., temperature sensors 4 are arranged along the strand 2. The means 4, 5 acquires, i.e., detects or calculates the state variable of the strand or the continuous casting installation and communicates them to the control or regulation unit 3 which based on the signals and/or data, dynamically evaluates the control temperature or temperatures of the strand 2 and, based on the same, controls achievement of the set temperature in respective regions of the strand 2. According to the invention, the change of the control or set temperature is effective in such a way that a dynamic adaptation of the set temperature is effected dependent on the given temperatures of the cast strand 2. Advantageously, calculation of the temperature of the cast strand is effected, and regulation of cooling or of the amount of spray water is carried out in order to achieve the set temperature by regulation. Advantageously, a catalogue of temperature curves is used. According to the invention, advantageously, a monitoring module of the temperature calculation is provided, and in this monitoring module, bulging, ductility, and shifting of the through solidification to the installation end is determined. The determined values are compared with the threshold values and either a warning is issued and/or a dynamic adaptation of the set temperature or set temperatures is undertaken. To this end, limiting is made to
It is advantageous, when the thermal stresses in the strand shell are reduced at the mold outlet. It is further advantageous when the control or regulation reduces or prevents operational states in which bulging of the strand between rollers becomes too big. It is also advantageous when the control or regulation reduces or prevents operational states in which the strand is bent or straightened in temperature region in which the strand material is brittle. In addition, it is advantageous when the control or regulation of the solidification length of the strand is monitored and, preferably, prevented or reduced to a most possible extent so that the solidification length of the strand is not longer than the distance to the end of the strand support, so that the strand is essentially already solidified behind the end of the strand support.
The inventive control method of controlling or regulating the temperature during secondary cooling of the cast strand is based on the temperature regulation, wherein at least one, however, preferably, several set temperature distributions for the strand surface are stored as selected preset values in a memory of the control or regulation unit.
In addition, it is available in the control or regulation unit 3, a stored data set such as, e.g., a chart in which a suitable set temperature distribution is associated with each usable material or with each usable or treatable group of material.
The control and regulation unit 3 controls, based on stored and selected data, the amounts of cooling water for secondary cooling so that the strand temperatures at least essentially correspond to set temperatures.
According to the invention, the control or regulation is so optimized that the set temperature distribution of the strand is not fixed for all operational states and, thus, is not binding, but rather the set temperature distribution is dynamically adapted according to predetermined criteria.
The control or regulation unit contains, in addition to calculation of strand temperatures and the primary control unit for setting water amounts, advantageously, also further modules for effecting additional tasks.
Advantageously, the discharge temperature of the strand discharged from the mold or at cooling segment following the mold, is calculated.
The set temperatures of the strand for the first cooling segment are then adapted to the determined discharge temperature. Thereby, a uniform cooling profile is obtained for strand, together with reduction of the thermal stresses.
Further, bulging of the strand can be calculated and, additionally, an allowable bulging of the strand can be determined. The allowable bulging can depend, e.g., from instantaneous process parameters of the continuous casting installation.
The control or regulation unit 3 compares, during casting, preferably continuously or with intervals, the detected or calculated bulge of the cast strand with a maximum allowable value. If this value is exceeded, the set temperature is reduced. The set temperature is preferably so reduced in the region of the cast strand where the excess is recognized, wherein, if necessary, the set temperature can also be reduced in a stretch in front.
According to the inventive idea, a further calculation module in the control or regulation unit 3 can determine the ductility of the strand. A comparison between a predetermined value of ductility with an allowable minimal value can be carried out. If this threshold value of the ductility in the bending or straightening unit is exceeded, the set temperature is increased by the control or regulation unit, wherein this preferably takes place at least in the cooling segment in front of the region of the bending or straightening unit. With regard to the above, limiting is made to
Further, according to an embodiment of the invention, the control or regulation unit 3 can calculate or determine the solidification length of the strand 2 and monitor it based on sensor signals. Because the strand is supported by support segments, it is expedient when the solidification length does not exceed the maximal distance of the last supporting segment in the displacement direction. Thereby, advantageously, the strand is already solidified before it leaves the last supporting segments. The solidification length for the strand according to a predetermined threshold value ends before the last segment. The threshold value can be monitored with a sensor, so that upon the solidification length exceeding the threshold value, the control or regulation unit 3 carries out counter-control measures. Based on the current dynamic behavior, the expected solidification length is assessed. When the solidification length of the strand exceeds the threshold value, the control or regulation unit causes reduction of the set temperature at least in one region before the solidification length reaches the threshold value so that the solidification length is reduced. This is caused by a strong strand cooling which makes the solidification length shorter. The threshold advantageously is so selected that during the control or regulation process, the solidification length does not exceed or does not substantially exceed the threshold value, and ends behind the supporting segments. In connection with this, limiting is made to
It should be explicitly pointed out that the process sequences shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 058 109 | Dec 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/010076 | 11/27/2008 | WO | 00 | 8/27/2010 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2009/071236 | 6/11/2009 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3358743 | Adams | Dec 1967 | A |
| 4030531 | Wunnenberg | Jun 1977 | A |
| 4463795 | Chielens | Aug 1984 | A |
| 5988259 | Welker et al. | Nov 1999 | A |
| 6225609 | Imanari et al. | May 2001 | B1 |
| 6386271 | Kawamoto et al. | May 2002 | B1 |
| 6880616 | Kemna | Apr 2005 | B1 |
| 6885907 | Zhang et al. | Apr 2005 | B1 |
| 20020050336 | Ebisu et al. | May 2002 | A1 |
| 20020189782 | Ashburn | Dec 2002 | A1 |
| 20070251663 | Sheldon et al. | Nov 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 2444443 | Sep 1974 | DE |
| 4417221 | Nov 1994 | DE |
| 4417808 | Dec 1994 | DE |
| 10255550 | Jan 2004 | DE |
| 102005049151 | Apr 2007 | DE |
| 1289691 | Jun 2001 | EP |
| 1550523 | Jul 2005 | EP |
| 1731243 | Dec 2006 | EP |
| 56151155 | Nov 1981 | JP |
| WO 2005120747 | Dec 2005 | WO |
| Entry |
|---|
| Ha et al. (Numerical Analysis of secondary cooling and bulging in the continuous casting of slabs, 2001). |
| Brimacombe (The Challenge of Quality in Continuous Casting Processes, 1996). |
| Sengupta et al., Understanding the Role Water Cooling Plays during Continuous Casting of Steel and Aluminum Alloys, 2004). |
| Hoedle et al., Advanced Equipment for High Performance Casters, MPT International Mar. 2003, pp. 74-80. |
| Moerwald et al., Roll Load Measurement on Thin Slab Caster for Liquid Core Detection, Ironmaking and Steelmaking, 1998, V. 25, No. 2, pp. 159-162. |
| Narzt et al., Produktinnovationen und Qualitaetsverbesserungen beim Brammenstranggiessen, stahl und eisen 123 (2003) No. 5, pp. 77-82. |
| Number | Date | Country | |
|---|---|---|---|
| 20100324721 A1 | Dec 2010 | US |
